1. Field of the Invention
The present invention relates to a cleaning device used for removing residual attachments from a surface of an intermediate transfer element onto which toner images are transferred from at least one image carrier. The invention also relates to an image forming apparatus including the cleaning device. The present invention further relates to a method of removing residual attachments from a surface of an intermediate transfer element.
2. Discussion of the Related Art
In the related art, there are two types of image forming apparatuses: a mono-color image forming apparatus, and a multi-color image forming apparatus. In a multi-color image forming apparatus, multi-color images are formed by two types of multi-color image forming methods, for example: (1) toner images of different colors are transferred from respective image carriers onto a transfer material while being each superimposed thereon, and (2) toner images of different colors are sequentially transferred from at least one image carrier onto an intermediate transfer element while being each superimposed thereon, and then a superimposed color toner image is transferred from the intermediate transfer element onto a transfer material.
In the case of using an intermediate transfer element, substances, such as toner, paper powders, or various types of additives, typically adhere onto a photoreceptor functioning as an image carrier or an intermediate transfer element after toner images are transferred therefrom. For example, if paper powders remain on an intermediate transfer element, a surface of a photoreceptor that contacts the intermediate transfer element may be damaged by the residual paper powders. As a result, background fouling typically occurs on the resultant images due to bad cleaning of the photoreceptor.
Some devices use a cleaning blade that contacts a surface of a photoreceptor or an intermediate transfer element to remove residual attachments remaining on the surface of the photoreceptor or the intermediate transfer element. For example, Japanese Utility Model Publication No 3-58668 and published Japanese patent application No. 5-323846 each describe a cleaning device including a cleaning blade that contacts a surface of a photoreceptor, and an elastic plate. An edge portion of the elastic plate periodically slides on an edge portion of the cleaning blade to remove attachments accumulated on the edge portion of the cleaning blade.
Japanese patent No. 2759813 describes a cleaning device including a cleaning blade that contacts a surface of a photoreceptor, and a rotary brush member that contacts an edge portion of the cleaning blade to remove attachments accumulated on the edge portion of the cleaning blade. Moreover, in some conventional systems, the polarity of residual toner remaining on a surface of a photoreceptor or an intermediate transfer element is uniformed by using a cleaning brush to enhance a removability of the residual toner. By doing so, an electrostatic transfer efficiency of toner may be enhanced in a subsequent cleaning process.
It is known that if a bias having a predetermined polarity is applied to the residual attachments on the intermediate transfer element by using a cleaning brush, the removability of residual toner may be enhanced, but the removability of the residual attachments other than toner, such as paper powders, may be unchanged. If such attachments remain on the intermediate transfer element and if the linear velocity of the intermediate transfer element is different from that of a photoreceptor, a surface of the photoreceptor is rubbed against the attachments remaining on the intermediate transfer element, and is damaged.
If the surface of the photoreceptor is damaged, a cleaning device may not effectively clean the damaged surface of the photoreceptor, thereby causing background fouling on the resultant images due to bad cleaning of the photoreceptor. If residual attachments are removed from a photoreceptor by contacting a leading edge portion of a cleaning blade to the surface of the photoreceptor, toner blocked by the cleaning blade accumulates on the leading edge portion of the cleaning blade. When an impacting force is applied to the accumulated toner, the accumulated toner easily falls from the leading edge portion of the cleaning blade by gravity, and may fall on an image carried on an intermediate transfer element. As a result, an abnormal image typically occurs due to mixture of the fallen toner and the image carried on the intermediate transfer element.
In some conventional systems, a releasing agent is applied onto a surface of a photoreceptor or an intermediate transfer element to prevent foreign substances from adhering onto the surface thereof by decreasing a coefficient of friction of the surface thereof. However, it may be difficult to uniform a coefficient of friction of a surface of a photoreceptor or an intermediate transfer element in a short period of time, and the coefficient of friction of the surface thereof may change with time. Considering the cost consumed for providing a releasing agent application device, a desired advantage may not be obtained.
Therefore, as discovered by the present inventors, it is desirable to provide a cleaning device and an image forming apparatus including the cleaning device that can exert a good cleaning performance on residual attachments on an intermediate transfer element and can control occurrences of background fouling and an abnormal image.
Further, it is desirable to provide a method of removing residual attachments from a surface of an intermediate transfer element while exerting a good cleaning performance on residual attachments on an intermediate transfer element and while controlling occurrences of background fouling and an abnormal image.